Wireless communication method and device

ABSTRACT

A wireless communication method and device are provided. The wireless communication method includes the steps of receiving a plurality of measurement results; determining whether a cell-change event is triggered according to the measurement results; calculating a reverse-direction criterion to determine whether a ping-pong effect will occur when the cell-change event is triggered; and terminating the cell-change event when the ping-pong effect will occur.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application claims priority of U.S. Provisional Patent Application No. 62/081,692, filed on Nov. 19, 2014 and Provisional Patent Application No. 62/194,368, filed on Jul. 20, 2015, the entirety of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to a wireless communication technology, and more particularly, to a wireless communication method for avoiding the ping-pong effect when cell reselection (CR) or handover (HO) is triggered.

2. Description of the Related Art

Wireless communication systems have been used widely to provide various telecommunication services such as telephony, video, data, messaging, and broadcast services. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmission power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency divisional multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by the Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrums, and integrating better with other open standards using OFDMA on downlinks (DL), and SC-FDMA on uplinks (UL) and multiple-input multiple-output (MIMO) antenna technology.

When user equipment (UE) needs to change a cell, the cell reselection (CR) or handover (HO) procedure will be performed. However, when the UE frequently switches serving cells between multiple cells within a short period of time, a ping-pong effect will occur. The ping-pong effect may result in excessive power consumption and a poor user experience. Therefore, how to avoid the ping-pong effect when the UE needs to change cells is a subject worthy of discussion.

BRIEF SUMMARY OF THE INVENTION

A wireless communication method and device are provided to overcome the problems mentioned above.

An embodiment of the invention provides a wireless communication method. The wireless communication method comprises the steps of receiving a plurality of measurement results; determining whether a cell-change event is triggered according to the measurement results; calculating a reverse-direction criterion to determine whether a ping-pong effect will occur when the cell-change event is triggered; and terminating the cell-change event when the ping-pong effect will occur during the reverse-direction.

An embodiment of the invention provides a wireless communication device. The wireless communication device comprises a processor. The processor is configured to determine whether a cell-change event is triggered according to measurement results, and calculate a reverse-direction criterion to determine whether a ping-pong effect will occur when the cell-change event is triggered, wherein the processor terminate the cell-change event when the ping-pong effect will occur.

Other aspects and features of the invention will become apparent to those with ordinary skill in the art upon review of the following descriptions of specific embodiments of methods and systems.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more fully understood by referring to the following detailed description with reference to the accompanying drawings, wherein:

FIG. 1 is a block diagram of a mobile communications system 100 according to an embodiment of the invention;

FIG. 2 is a schematic diagram illustrating the reverse-direction criterion check for cell reselection for IRAT according to an embodiment of the invention;

FIG. 3 is a schematic diagram illustrating the reverse-direction criterion check for cell reselection for INTRA-LTE according to an embodiment of the invention;

FIG. 4 is a schematic diagram illustrating the reverse-direction criterion check for handover according to an embodiment of the invention;

FIG. 5A is a schematic diagram illustrating the ping-pong effect for multiple cells according to an embodiment of the invention;

FIG. 5B is a schematic diagram illustrating the ping-pong effect for multiple cells according to another embodiment of the invention

FIGS. 6A-6B is a flow chart illustrating the wireless communication method for cell reselection according to an embodiment of the invention;

FIG. 7 is a flow chart illustrating the wireless communication method for handover according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.

FIG. 1 is a block diagram of a mobile communications system 100 according to an embodiment of the invention. The system 100 comprises User Equipment (UE) 110 and a service network 120. The UE 110 may be a mobile communications device, such as a cellular phone, a smartphone modem processor, a data card, a laptop stick, a mobile hotspot, a USB modem, a tablet, etc.

The UE 110 may comprise at least a baseband signal processing device 111, a radio frequency (RF) signal processing device 112, a processor 113, a memory device 114, and an antenna module comprising at least one antenna. Note that, in order to clarify the concept of the invention, FIG. 1 presents a simplified block diagram in which only the elements relevant to the invention are shown. However, the invention should not be limited to what is shown in FIG. 1.

The RF signal processing device 112 may receive RF signals via the antenna and process the received RF signals to convert the received RF signals to baseband signals to be processed by the baseband signal processing device 111, or receive baseband signals from the baseband signal processing device 111 and convert the received baseband signals to RF signals to be transmitted to a peer communications apparatus. The RF signal processing device 112 may comprise a plurality of hardware elements to perform radio frequency conversion. For example, the RF signal processing device 112 may comprise a power amplifier, a mixer, etc.

The baseband signal processing device 111 may further process the baseband signals to obtain information or data transmitted by the peer communications apparatus. The baseband signal processing device 111 may also comprise a plurality of hardware elements to perform baseband signal processing. The baseband signal processing may comprise analog-to-digital conversion (ADC)/digital-to-analog conversion (DAC), gain adjustment, modulation/demodulation, encoding/decoding, and so on.

The processor 113 may control the operations of the baseband signal processing device 111 and the RF signal processing device 112. According to an embodiment of the invention, the processor 113 may also be arranged to execute the program codes of the software module(s) of the corresponding baseband signal processing device 111 and/or the RF signal processing device 112. The program codes accompanied by specific data in a data structure may also be referred to as a processor logic unit or a stack instance when being executed. Therefore, the processor 113 may be regarded as being comprised of a plurality of processor logic units, each for executing one or more specific functions or tasks of the corresponding software module(s).

The memory device 114 may store the software and firmware program codes, system data, user data, etc. of the UE 110. The memory device 114 may be a volatile memory such as a Random Access Memory (RAM); a non-volatile memory such as a flash memory or Read-Only Memory (ROM); a hard disk; or any combination thereof.

According to an embodiment of the invention, the RF signal processing device 112 and the baseband signal processing device 111 may collectively be regarded as a radio module capable of communicating with a wireless network to provide wireless communications services in compliance with a predetermined Radio Access Technology (RAT). Note that, in some embodiments of the invention, the UE 110 may be extended further to comprise more than one antenna and/or more than one radio module, and the invention should not be limited to what is shown in FIG. 1.

In addition, in some embodiments of the invention, the processor 113 may be configured inside of the baseband signal processing device 111, or the UE 110 may comprise another processor configured inside of the baseband signal processing device 111. Thus the invention should not be limited to the architecture shown in FIG. 1.

The service network 120 may comprise a GSM EDGE Radio Access Network (GERAN) 130, a Universal Terrestrial Radio Access Network (UTRAN) 140, an Evolved UTRAN (E-UTRAN) 150, a General Packet Radio Service (GPRS) subsystem 160 and an Evolved Packet Core (EPC) subsystem 170. The GERAN 130, UTRAN 140 and E-UTRAN 150 may be in communication with the GPRS subsystem 160 or the EPC subsystem 170, wherein the GERAN 130, UTRAN 140 and E-UTRAN 150 allow connectivity between the UE 110 and the GPRS subsystem 160 or the EPC subsystem 170 by providing the functionality of wireless transmission and reception to and from the UE 110 for the GPRS subsystem 160 or the EPC subsystem 170, and the GPRS subsystem 160 or the EPC subsystem 170 signals the required operation to the GERAN 130, UTRAN 140 and E-UTRAN 150 for providing wireless services to the UE 110. The GERAN 130, UTRAN 140 and E-UTRAN 150 may contain one or more base stations (or called NodeBs or eNodeBs) and Radio Network Controllers (RNCs). Specifically, the GPRS subsystem 160 includes a Serving GPRS (General Packet Radio Services) Support Node (SGSN) 161 and a Gateway GPRS Support Node (GGSN) 162, wherein the SGSN 161 is the key control node for packet routing and transfer, mobility management (e.g., attach/detach and location management), session management, logical link management, and authentication and charging functions, etc., and the GGSN 162 is responsible for Packet Data Protocol (PDP) address assignments and interoperability with external networks. The EPC subsystem 170 may comprise a Mobility Management Entity (MME) 171, which may be responsible for idle mode UE tracking, paging procedures, and attachment and activation processes. The EPC subsystem 170 may also comprise a Servicing Gateway (SGW) 172, which may be responsible for the routing and forwarding of data packets. The EPC subsystem 170 may also include a Packet data network Gateway (PGW) 173, which may be responsible for providing connectivity from the UE 110 to external networks. Both the SGSN 161 and the MME 171 may be in communication with Home Subscriber Server (HSS) 180 which may provide device identification information, an International Mobile Subscriber Identity (IMSI), etc. It should be appreciated that the EPC subsystem 170 may also comprise a S4-SGSN 175, thereby allowing the GERAN 130 or UTRAN 140 to be accessed when the GPRS subsystem 160 is replaced by the EPC subsystem 170. Additionally, the service network 120 may also include other functional entities, such as a Home Location Register (HLR) (not shown) which is a central database storing user-related and subscription-related information, and the invention is not limited thereto. In an embodiment of the invention, the service network 120 may also comprise a Code Division Multiple Access (CDMA) network.

In an embodiment of the invention, the processor 113 may determine whether a cell-change event is triggered according to the receiving measurement results of neighboring cells, wherein the cell-change event may be cell reselection (CR) or handover (HO). When the UE 110 is in an idle mode, the UE 110 may perform cell reselection to change cell according the criteria provided by system information. When the UE 110 in connected mode, the cell-change is controlled by the network 120. Specifically, the UE 110 may transmit measurement report to the network 120 first. When the network 120 receives the measurement report from UE 110, the network 120 may determine whether to perform a handover according to the measurement report. The measurement report may correspond to a specific event, such as A3, B2, and A2. For general used case, the event A3 is configured to trigger the LTE handover, event B2 is configured to trigger the inter radio access technology (IRAT) handover and event is A2 configured to trigger the redirection. It is should be understood that the invention is not limited to above specific events.

When the cell-change event is triggered, the processor 113 will perform a reverse-direction criterion calculation to check whether a reverse-direction criterion satisfies a condition for changing cells. Then, the processor 113 will determine whether a ping-pong effect may occur according to the checking result. In an embodiment of the invention, when the checking result indicates that the reverse-direction criterion is satisfied for changing cells, i.e. the cell-change event will also be triggered in the reverse direction, the processor 113 determines that the ping-pong effect will occur. When the checking result indicates that the reverse-direction criterion is not satisfied for changing cells, i.e. the cell-change event will not be triggered in reverse direction, the processor 113 determines that the ping-pong effect will not occur. The details are discussed below. In an embodiment of the invention, when the processor 113 determines that the ping-pong effect will occur, the processor 113 will terminate the cell-change procedure (cell reselection or handover).

In an embodiment of the invention, for cases of cell reselection (CR), the processor 113 checks whether the reverse-direction criterion is satisfied for changing cells according to the stored system information corresponding to a target cell to determine whether the ping-pong effect will occur. In an embodiment of the invention, for 4G radio access technology, the necessary system information include SystemInformationBlockType1 (SIB1), SystemInformationBlockType3 (SIB3), SystemInformationBlockType4 (SIB4), SystemInformationBlockType5 (SIB5) for intra-LTE cell reselection, and additional SystemInformationBlockType6 (SIB6), SystemInformationBlockType7 (SIB7) is needed for inter radio access technology (IRAT) cell reselection. In an embodiment of the invention, for 3G radio access technology, the system information can be Master Information Block (MIB) and SystemInformationBlockType19 (SIB19). In an embodiment of the invention, for 2G radio access technology, the system information can be SI2Quater, SI3.

In an embodiment of the invention, the memory device 114 may store the system information which the UE 110 has previously collected, and the collected system information will be regarded as the stored system information. In an embodiment of the invention, when the processor 113 cannot obtain the stored system information for the target cell, i.e. the memory device 114 does not have the system information for the target cell, the processor 113 may perform evaluation phase to get the system information for the target cell in an evaluation phase before the cell reselection is performed. The system information will be obtained in the evaluation phase.

In an embodiment of the invention, the cell reselection is for inter radio access technology (IRAT) cell change, i.e. the current cell which the UE 110 is camping on and the target cell corresponds to different radio access technologies. When the IRAT cell reselection is triggered, the processor 113 may perform an evaluation (i.e. in an evaluation phase) to prepare the cell reselection before radio access technology (RAT) changes. Then, the processor 113 may check whether the reverse-direction criterion is satisfied according to the stored system information of the target cell. If the reverse-direction criterion is satisfied for changing cells, the processor 113 will terminate (or fail) the evaluation, i.e. the radio access technology (RAT) will not change. If the reverse-direction criterion is not satisfied for changing cells, the IRAT cell resection procedure will continue.

In an embodiment of the invention, if the evaluation is terminated because the reverse-direction criterion is satisfied for changing cells, the processor 113 may remove the target cell or target frequency for the evaluation from a candidate cell list for a time period on the current radio access technology to avoid retrying the target cell frequently. In an embodiment of the invention, the processor 113 may initiate a timer that corresponds to the time period. The target cell or the frequency for the evaluation will not be used until the timer expires.

In an embodiment of the invention, when the ping-pong is detected (i.e. the reverse-direction criterion is satisfied), the processor 113 may keep the UE 110 in a preferred RAT. The preferred RAT means the RAT with a higher priority. For example, if the RAT for a 4G network has a higher priority than the RAT for a 3G network, the RAT for 4G may regarded as the preferred RAT. When the ping-pong is detected and the target RAT is the preferred RAT, the processor 133 may still change the current RAT to the target RAT. Therefore, in an embodiment of the invention, if the cell reselection is for inter radio access technology (IRAT), the processor 113 may determine whether the current RAT is a preferred RAT and whether the current RAT has good signal quality first. Only when the current RAT is the preferred RAT and the current RAT has good signal quality, will the processor 113 check the reverse-direction criterion. When the current RAT is not the preferred RAT or the current RAT does not have good signal quality, the processor 113 will not check the reverse-direction criterion.

FIG. 2 is a schematic diagram illustrating the reverse-direction criterion check for IRAT cell reselection according to an embodiment of the invention. As shown in FIG. 2, the current radio access technology (current RAT) is LTE (4G) and the target radio access technology (target RAT) is UMTS (3G). When a cell reselection procedure from 4G to 3G is triggered, in the evaluation phase, the processor 113 may transmit a 4G3 IRCR evaluation Request message from the current RAT to the target RAT. Then, in the target RAT, the processor 113 may check whether the reverse direction (from 3G to 4G) criterion is satisfied for changing cells according to the stored system information for the target cell of the target RAT. When the reverse-direction criterion is satisfied for changing cells, the processor 113 will determine that the ping-pong effect will occur (i.e. the ping-pong is detected) and terminate (or fail) the evaluation. Then, the processor 113 may transmit a 4G3 IRCR evaluation Cnf message from the target RAT to the current RAT to notify the current RAT that the evaluation has failed. When the current RAT obtains the 4G3 IRCR evaluation Cnf message, the processor 113 will remove the target cell or the target frequency for the evaluation form a candidate cell list for a time period.

In another embodiment of the invention, the cell reselection is for intra long term evolution (INTRA-LTE), i.e. the target cell and current cell are for the same radio access technology (i.e. LTE). If the cell reselection for intra long term evolution is triggered, when the target cell satisfies a cell-reselection criterion (i.e. the target cell's signal strength and quality meets the cell-reselection criterion), the processor 113 may check whether the reverse-direction criterion is satisfied according to the stored system information to determine whether the ping-pong effect will occur. When the reverse-direction criterion is satisfied, the processor 113 may remove the target cell from a candidate cell list.

In an embodiment of the invention, if the cell reselection is for intra long term evolution (INTRA-LTE), the processor 113 may select a cell which has better signal strength to camp on when processor 113 determines that the ping-pong effect will occur.

FIG. 3 is a schematic diagram illustrating the reverse-direction criterion check for cell reselection for INTRA-LTE according to an embodiment of the invention. As shown in FIG. 3, the current cell is the LTE cell A and the target cell is the LTE cell B. When the processor 113 receives the measurement result of the LTE cell B, the processor 113 will determine whether the INTRA-LTE cell reselection is triggered. If it is triggered, the processor 113 will check whether the reverse-direction criterion satisfies the condition according to the stored system information to determine whether the ping-pong effect will occur. When the reverse-direction criterion is satisfied, the processor 113 may determine the ping-pong effect will occur (i.e. the ping-pong is detected) and remove the LTE cell B from a candidate cell list. In an embodiment of the invention, the processor 113 may select a cell which has better signal strength to camp on when the ping-pong effect will occur.

In an embodiment of the invention, for cases of cell reselection, the processor 113 may perform a cell global ID check in the evaluation phase to avoid any physical cell identity (PCI) confusion. For INTRA-LTE, the processor 113 can obtain the cell global ID of the target cell from the SystemInformationBlockType1 (SIB 1). For 4G to 3G cell reselection, the processor 113 can obtain the cell global ID of the target cell from the MIB. For 4G to 2G cell reselection, the processor 113 can obtain the cell global ID of the target cell from the SI3. The processor can confirm whether the ID information of the target cell from the stored information is the same as the cell global ID of the target. In another embodiment of the invention, the processor 113 may check location information to avoid PCI confusion. The location information may be tracking area code (TAC) information, location area code (LAC) information, routing area code (RAC) information, and global positioning system (GPS) information. In another embodiment of the invention, the processor 113 may check history information to avoid PCI confusion.

In an embodiment of the in invention, for cases of handover (HO), the processor 113 may check whether the reverse-direction criterion is satisfied for changing cells according to stored measurement parameters from a target cell to determine whether the ping-pong effect will occur. If the reverse-direction criterion is satisfied for changing cells, the processor 113 will determine that the ping-pong effect will occur.

In an embodiment of the invention, if the handover is for inter radio access technology (IRAT), the processor 113 may check whether the reverse-direction criterion is satisfied according to the stored measurement parameters from the target cell before a measurement report (e.g. event B2) for triggering the handover is transmitted from the UE 110 to a network of a current radio access technology. That is to say, the check of the reverse-direction criterion is performed before the measurement report is transmitted from UE 110 to the network of the current radio access technology to trigger the handover. When the reverse-direction criterion is satisfied, the processor 113 may forbid the transmission of the measurement report to the network of the current radio access technology.

In an embodiment of the invention, if the memory device does not store the stored measurement parameters for the target cell, the processor 113 may continue the handover procedure (i.e. transmit the measurement report to the network).

In an embodiment of the invention, when the ping-pong is detected (i.e. the reverse-direction criterion is satisfied), the processor 113 may keep the UE 110 in a preferred RAT. The preferred RAT means the RAT with a higher priority. For example, if the RAT for the 4G network has a higher priority than the RAT for the 3G network, the RAT for 4G may regarded as the preferred RAT. When the ping-pong is detected and the target RAT is the preferred RAT, the processor 133 may still change the current RAT to the target RAT. Therefore, in an embodiment of the invention, if the handover is for inter radio access technology (IRAT), the processor 113 may first determine whether the current RAT is a preferred RAT and whether the current RAT has good signal quality. Only when the current RAT is the preferred RAT and the current RAT has good signal quality will the processor 113 check the reverse-direction criterion. When the current RAT is not the preferred RAT or the current RAT does not have good signal quality, the processor 113 will not check the reverse-direction criterion.

In an embodiment of the invention, if the handover is for intra long term evolution (INTRA-LTE), the processor 113 may check whether the reverse-direction criterion is satisfied according to the stored measurement parameters for the target cell before a measurement report for triggering the handover is transmitted to the network of a current radio access technology. When the reverse-direction criterion is satisfied, the processor 113 may forbid the transmission of the measurement report to the network of the current radio access technology.

In an embodiment of the invention, if the cell handover is for intra long term evolution (INTRA-LTE), the processor 113 may select a cell which has better signal strength to camp on when the processor 113 determines that the ping-pong effect will occur.

FIG. 4 is a schematic diagram illustrating the reverse-direction criterion check for handover according to an embodiment of the invention. As shown in FIG. 4, the current cell is the LTE cell A and the target cell is the cell B where the LTE cell A and the cell B may correspond to the same RAT (INTRA-LTE) or different RATs (IRAT). When the processor 113 receives the measurement result from the cell B, the processor 113 will determine whether the measurement report for INTRA-LTE or IRAT is triggered. If the measurement report for INTRA-LTE or IRAT is triggered, the processor 113 will check whether the reverse-direction criterion is satisfied according to the measurement parameters from the cell B to determine whether the ping-pong effect will occur. When the reverse-direction criterion is satisfied, the processor 113 may determine the ping-pong effect will occur and forbid the transmission of the measurement report (HO event report) to the network.

Because the ping-pong effect may be more complex, such as the ping-pong effect taking place between more than two cells. For example, as shown in FIG. 5A, the ping-pong effect does not occur between the 4G cell 1 and 4G cell 2, between the 4G cell 2 and 4G cell 3, and between the 4G cell 3 and 4G cell 1. However, the ping-pong effect will occur every three 4G cells. For another example, as shown in FIG. 5B, the ping-pong effect does not occur between the 4G cell 1 and 3G cell 1, between the 3G cell 1 and 4G cell 3, and between the 4G cell 3 and 4G cell 1. However, the ping-pong effect will occur every three 4G cells. Therefore, in an embodiment of the invention, when the processor 133 determine the pin-pong effect will not occur between two cells, the processor 133 may further check whether a multiple-cell ping-pong (not limited to three cells) will occur according to cell-change history information and stored system information.

FIGS. 6A-6B is a flow chart illustrating the wireless communication method for cell reselection according to an embodiment of the invention. The wireless communication method is applied to the UE 110. First, in step S610, the UE 110 receives a plurality of measurement results from neighboring cells. In step S620, the UE 110 may determine whether the cell reselection is triggered according to the measurement results. If the UE 110 determines that cell reselection is not triggered according to the measurement results, the method returns to step S620. If the UE 110 determines that cell reselection is triggered according to the measurement results, step S630 will be performed. In step S630, the UE 110 may determine whether the stored system information can be obtained.

If the stored system information can be obtained, step S640 will be performed. In step S640, the UE 110 may determine whether there is any related information to avoid any physical cell identity (PCI) confusion. If related information to avoid PCI confusion can be obtained, the UE 110 may perform a cell global ID check or check location information or history information to avoid PCI confusion (step S650). If related information to avoid PCI confusion cannot be obtained, step S660 may be performed. In step S660, the processor 113 may perform an evaluation (i.e. in evaluation phase) before the cell reselection is executed, wherein system information (comprising the related information to avoid PCI confusion) for a target cell will be obtained in the evaluation phase. If the stored system information cannot be obtained, the processor will also perform step S660.

Then, in step S670, the UE 110 may calculate a reverse-direction criterion to determine whether a ping-pong effect will occur. When the reverse-direction criterion is satisfied, the UE 110 will determine that the ping-pong effect will occur. When the UE 110 determines that the ping-pong effect will occur, step S680 will be performed. In step S680, the UE 110 may determine not to perform the cell reselection.

When the reverse-direction criterion is not satisfied, the UE 110 will further determine whether the ping-pong effect for multiple cells will occur according to the cell change history information (S690). If the ping-pong effect for multiple cells will occur, the UE 110 will not perform the cell reselection (S680). If the ping-pong effect for multiple cells will not occur, the UE 110 will continue to perform cell reselection (step S6100). In an embodiment of the invention, if the UE 110 cannot obtain the cell change history information in step S690, the UE will perform cell reselection (S6100).

FIG. 7 is a flow chart illustrating the wireless communication method for handover according to an embodiment of the invention. The wireless communication method is applied to the UE 110. First, in step S710, the UE 110 receives a plurality of measurement results from neighboring cells. In step S720, the UE 110 may determine whether the handover is triggered according to the measurement results. If the UE 110 determines that handover is not triggered according to the measurement results, the method returns to step S720. If the UE 110 determines that handover is triggered according to the measurement results, step S730 will be performed. In step S730, the UE 110 may determine whether the stored measurement parameters for the target cell can be obtained.

If the stored system information can be obtained, step S740 will be performed. In step S740, the UE 110 may calculate a reverse-direction criterion to determine whether a ping-pong effect will occur. When the reverse-direction criterion is satisfied, the UE 110 will determine that the ping-pong effect will occur. When the UE 110 determines that the ping-pong effect will occur, step S750 will be performed. In step S750, the UE 110 may determine not to transmit the measurement report to the network to trigger the handover. If the stored measurement parameter cannot be obtained, step S760 will be performed. In step S760, the UE 110 will transmit the measurement report to the network to trigger the handover.

When the reverse-direction criterion is not satisfied for changing cells, the UE 110 will further determine whether the ping-pong effect for multiple cells will occur according to the cell change history information (S770). If the ping-pong effect for multiple cells will occur, the UE 110 will perform step 750. If the ping-pong effect for multiple cells will not occur, the UE 110 will continue to perform step S760.

In the wireless communication method of the invention, the ping-pong effect can be avoided by the reverse-direction criterion check.

The steps of the method described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module (e.g., including executable instructions and related data) and other data may reside in a data memory such as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of computer-readable storage medium known in the art. A sample storage medium may be coupled to a machine such as, for example, a computer/processor (which may be referred to herein, for convenience, as a “processor”) such that the processor can read information (e.g., code) from and write information to the storage medium. A sample storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in user equipment. In the alternative, the processor and the storage medium may reside as discrete components in user equipment. Moreover, in some aspects, any suitable computer-program product may comprise a computer-readable medium comprising codes relating to one or more of the aspects of the disclosure. In some aspects, a computer software product may comprise packaging materials.

It should be noted that although not explicitly specified, one or more steps of the methods described herein can include a step for storing, displaying and/or outputting as required for a particular application. In other words, any data, records, fields, and/or intermediate results discussed in the methods can be stored, displayed, and/or output to another device as required for a particular application. While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention can be devised without departing from the basic scope thereof. Various embodiments presented herein, or portions thereof, can be combined to create further embodiments. The above description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.

The above paragraphs describe many aspects. Obviously, the teaching of the invention can be accomplished by many methods, and any specific configurations or functions in the disclosed embodiments only present a representative condition. Those who are skilled in this technology can understand that all of the disclosed aspects in the invention can be applied independently or be incorporated.

While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. Those who are skilled in this technology can still make various alterations and modifications without departing from the scope and spirit of this invention. Therefore, the scope of the present invention shall be defined and protected by the following claims and their equivalents. 

What is claimed is:
 1. A wireless communication method, comprising: receiving a plurality of measurement results; determining whether a cell-change event is triggered according to the measurement results; calculating a reverse-direction criterion to determine whether a ping-pong effect will occur when the cell-change event is triggered; and terminating the cell-change event when the ping-pong effect will occur.
 2. The wireless communication method of claim 1, wherein the cell-change event is a cell reselection (CR) or a handover (HO).
 3. The wireless communication method of claim 2, further comprising: checking whether the reverse-direction criterion is satisfied according to stored system information or stored measurement parameter to determine whether the ping-pong effect will occur.
 4. The wireless communication method of claim 2, further comprising: removing a target cell or a target frequency for an evaluation from a candidate cell list for a time period when the reverse-direction criterion is satisfied.
 5. The wireless communication method of claim 3, wherein if the cell reselection is for inter radio access technology (IRAT), the method further comprises: performing an evaluation for the cell reselection in an evaluation phase before radio access technology (RAT) changes, wherein system information for a target cell is obtained in the evaluation phase.
 6. The wireless communication method of claim 3, further comprising: performing a cell global ID check or checks location information or history information to avoid physical cell identity (PCI) confusion.
 7. The wireless communication method of claim 3, further comprising: forbidding transmission of a measurement report for triggering the handover to a target cell when the reverse-direction criterion is satisfied.
 8. The wireless communication method of claim 3, further comprising: performing handover when the stored measurement parameters for the target cell cannot be obtained.
 9. The wireless communication method of claim 1, wherein if the cell-change event is for inter radio access technology (IRAT), the method further comprises: determining whether a current radio access technology is a preferred radio access technology and whether the current radio access technology has good signal quality; and checking the reverse-direction criterion when the current radio access technology is the preferred radio access technology and the current radio access technology has good signal quality.
 10. The wireless communication method of claim 9, wherein when the current radio access technology is not the preferred radio access technology or the current radio access technology does not have good signal quality, the reverse-direction criterion will not be checked.
 11. The wireless communication method of claim 1, wherein if the cell-change event is for intra long term evolution (INTRA-LTE), the method further comprises: selecting a cell which has better signal strength to camp on when the ping-pong effect will occur.
 12. The wireless communication method of claim 1, further comprising: checking whether a multiple-cell ping-pong will occur according to cell-change history information and stored system information.
 13. A wireless communication device, comprising: a processor, configured to determine whether a cell-change event is triggered according to measurement results, and calculate a reverse-direction criterion to determine whether a ping-pong effect will occur when the cell-change event is triggered, wherein the processor terminates the cell-change event when the ping-pong effect will occur.
 14. The wireless communication device of claim 13, wherein the cell-change event is a cell reselection (CR) or a handover (HO).
 15. The wireless communication device of claim 14, wherein the processor further calculates whether the reverse-direction criterion is satisfied according to stored system information or stored measurement parameter to determine whether the ping-pong effect will occur.
 16. The wireless communication device of claim 14, wherein the processor further removes a target cell or a target frequency for an evaluation from a candidate cell list for a time period.
 17. The wireless communication device of claim 15, wherein if the cell reselection is for inter radio access technology (IRAT), the processor further performs an evaluation for the cell reselection in an evaluation phase before radio access technology (RAT) changes, wherein system information for a target cell is obtained in the evaluation phase.
 18. The wireless communication device of claim 15, wherein the processor further performs a cell global ID check or checks location information or history information to avoid physical cell identity (PCI) confusion.
 19. The wireless communication device of claim 15, wherein the processor further forbids the transmission of a measurement report for triggering the handover to technology target cell when the reverse-direction criterion is satisfied.
 20. The wireless communication device of claim 15, wherein the processor further performs handover when the stored measurement parameters for the target cell cannot be obtained.
 21. The wireless communication device of claim 13, wherein if the cell-change event is for inter radio access technology (IRAT), the processor further determines whether a current radio access technology is a preferred radio access technology and whether the current radio access technology has good signal quality, wherein when the current radio access technology is the preferred radio access technology and the current radio access technology has good signal quality, the processor checks the reverse-direction criterion.
 22. The wireless communication device of claim 21, wherein when the current radio access technology is not the preferred radio access technology or the current radio access technology does not have good signal quality, the processor will not check the reverse-direction criterion.
 23. The wireless communication device of claim 13, wherein if the cell-change event is for intra long term evolution (INTRA-LTE), the processor further selects a cell which has better signal strength to camp on.
 24. The wireless communication device of claim 13, wherein the processor further checks whether a multiple-cell ping-pong will occur according to cell-change history information and stored system information. 